There is great variation in the lengths of women's menstrual cycles. It is often the case that women would like to know the current phase of their menstrual cycle. Of particular interest to many is knowledge of when they are in the “fertile window” which occurs from approximately five days before ovulation until two days after ovulation. Typically, urine tests, calendar-based methods, and symptoms-based methods (in which parameters such as cervical mucus, cervical position, and basal body temperature are measured) are used for such determinations.